Labyrinth seal for fan assembly

ABSTRACT

Attaching a labyrinth seal composed of wear-resistant material to the surfaces of rotating equipment subject to wear can increase the life of the rotating equipment and reduce down-time for equipment maintenance and repairs.

BACKGROUND OF THE INVENTION

[0001] In rotating machines, such as turbines, power expanders, powerplant fans, pumps, and the like, a fluid, such as a liquid or gas isoften rotated through the machine. Frequently, the liquid or gascomponent contains suspended solids. When these solids strike againstthe exposed surfaces of the machine, it can cause accelerated wear onthe machine surfaces. This wear generally does not occur evenly, andgreater wear is seen in areas where the solids are projected against thesurface, or currents or eddies form in the gas or liquid stream,retaining a portion of the stream in contact with part surfaces for anextended time. Often, the solid material will completely wear away themachine parts, necessitating repair or replacement of the worn parts.Often, these assemblies are located deep inside machinery, and theentire system must be shut down and dismantled to gain access to wornparts. A longer time duration between machine shutdowns, which increasesproductivity and reduces down time, is desirable in these circumstances.

[0002] One solution to this wear problem has been to place a coating orliner on the exposed surfaces which are subject to wear to slow orreduce the wear. When the liners on the areas more subject to wear havedeteriorated, they can be replaced, eliminating the need to replace theentire part. However, thin coatings which are sprayed or painted on areoften insufficient to slow wear significantly enough to warrant theexpense and time of coating. Another solution has been to construct therotating equipment of a material that is more resistant to wear.However, this tends to be cost-prohibitive because such materials aregenerally expensive, and are only needed in areas where there is actualcontact of the solids with the surface. Yet another solution has been toattach a solid layer of wear-resistant material to the areas of themachinery that experience wear, or etching. However, difficulties haveoccurred with finding a means to adhere the wear-resistant material tothe wear areas of the rotating equipment that will provide sufficientadhesion during operation of the equipment, but that can be removed whenit becomes necessary to replace the wear-resistant material.Additionally, when a solid layer has been attached, difficulties haveoccurred with the solid material experiencing cracking or fracturefailures when the machine starts or stops because the solid material isnot flexible enough to withstand the torque applied during starting andstopping.

[0003] Therefore, what is needed is a means to slow or reduce wear inthe areas of rotating equipment which see the greatest wear that is ofsufficient durability that the equipment can go for long periods betweenreplacement of the wear-resisting means, while finding a material thatwill not experience fractures during machine starts and stops.

BRIEF SUMMARY OF THE INVENTION

[0004] Labyrinth seals are formed by layering, or lapping materials in away to deflect or slow the flow of materials, or minimize leakage ofmaterials through the seal. Labyrinth seals are frequently employed whenit is desired to keep materials in, or out of, certain areas ofequipment, such as keeping gases out of areas where sparks aregenerated, or keeping solids away from rotating drive shafts where thesolids could accumulate, and slow or stop rotation, or damage the shaftsby wear.

[0005] The present invention involves attaching a labyrinth seal to highwear areas in rotating machines to slow or reduce wear. The irregularlyshaped adjacent edges where the material is lapped help to alter thenormal turbulence paths across the surface of the rotating equipment,and thus reduce wear. Additionally, in areas that involve junctions oftwo parts, where the greatest amount of wear is generally seen, anadditional layer of labyrinth seal can be attached to the joint areas toslow or reduce wear in these areas even further. Because the labyrinthseal is comprised of individual tiles, the seal has sufficientflexibility to move slightly and therefore withstand cracking orfracturing when the fan is started and stopped.

[0006] The foregoing has outlined rather broadly the features andtechnical advantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiment disclosed may be readily utilized as a basisfor modifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a more complete understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich:

[0008]FIG. 1 is a perspective view of an installation of a coal-firedpower system fan embodying features of the present invention;

[0009]FIG. 2 is a side elevation view of the system of FIG. 1 takenalong the line 2-2 of FIG. 1;

[0010]FIG. 3 shows an expanded view of one arrangement of a labyrinthseal of the present invention fully installed on a fan blade;

[0011]FIG. 4 shows an expanded view of an alternative arrangement of alabyrinth seal of the present invention fully installed on a fan blade;

[0012]FIG. 5 is an expanded view of one arrangement of a labyrinth sealof the present invention partially mounted on a fan blade duringconstruction of the labyrinth seal;

[0013]FIG. 6 is an expanded view of one arrangement of a labyrinth sealof the present invention mounted on a fan blade during construction ofthe labyrinth seal;

[0014]FIG. 7 is an expanded view of an alterative arrangement of alabyrinth seal of the present invention partially mounted on a fan bladeduring construction of the labyrinth seal; and

[0015]FIG. 8 is an expanded view of an alternative arrangement of alabyrinth seal of the present invention mounted on a fan blade duringconstruction of the labyrinth seal.

DETAILED DESCRIPTION OF THE INVENTION

[0016] In the discussion of the FIGURES the same reference numerals willbe used throughout to refer to the same or similar components. In theinterest of conciseness, various components known to the art, such asmotors, combustion chambers, and the like, have not been shown ordiscussed. One arrangement of the present invention, the installation ofa labyrinth seal on a fan in a coal-fired power plant, is depicted anddescribed herein. It can be appreciated by those skilled in the art thatother arrangements and uses for the present invention not described indetail herein are also included within the scope of the presentinvention.

[0017]FIG. 1 shows an embodiment of the present invention, theinstallation of a labyrinth seal on portions of the fan in a coal-firedpower plant. The reference numeral 1 generally designates a fan systemassembly embodying features of the present invention. The system 1includes a fan 10, defining a non-sealed hub 12, and two sides 14comprising the outer perimeter of the fan. The fan also has a number offan blades 16 that extend from the hub to the outside circumference ofthe fan that are secured between the two sides 14 of the fan. Gas orliquid and suspended coal particles are drawn into the hub 12 of the fan10, and are projected out the circumference of the fan.

[0018] As shown in FIG. 2, channels 18 are formed by the fan blade 16and fan sides 14. When the gas or liquid containing solid particlesflows through the channels 18 of the fan 10, turbulence occurs, andincreased wear areas are seen, particularly along the channel edges,where the solids tend to accumulate out of the flow stream. The extendedcontact of the particles against these surfaces causes the surfaces towear away more quickly.

[0019] The areas subject to increased wear will vary based on the liquidor gas being projected through the channels 18, and the solids withinthat liquid or gas. By knowing where the greatest turbulence will occurin a particular machine, a labyrinth seal 100 can be designed andinstalled to minimize wear created by the friction. When the friction isreduced, wear in those areas is also reduced, resulting in a seal orliner that does not wear as quickly in those high stress areas. Becausethe seals slow part wear, decreased down time for replacement of sealsor machine parts results.

[0020] As shown in FIGS. 3 and 4, a labyrinth seal 100 can be attachedalong the surfaces of the fan blades 16 and fan sides 14 which arestruck most frequently by the suspended particles to reduce the wear.The labyrinth seal 100 is comprised of a series of plates 102 securelyattached to the fan sides 14 and the face of the fan blade 16 or asubstrate 20 that is secured to the face of the fan blade 16. The sealextends to cover the surfaces with which the gas or liquid and suspendedparticles come in contact and cause wear.

[0021] The plates may be attached by brazing or soldering, or by othermethods such as the use of an epoxy material, depending on the materialcomposition of the plates 102, the fan blade 16, and fan sides 14. Thematerial compositions and attachment methods also determine if asubstrate 20 should be inserted between the plates 102 and the fan blade16. The seal is comprised of a series of plates 102, rather than asingle sheet of material, because the edges of the plates 102 tend toreduce the turbulence of the gas or liquid across the surface of theseal 100 by breaking up the flow, whereas a single smooth surface wouldincrease the flow speed, causing additional wear on the labyrinth seal100. Additionally, individual plates can move slightly in relation toeach other, therefore withstanding the torque experienced when the fanstarts or stops without cracking or fracturing such as a single largesurface might experience.

[0022] The labyrinth seal 100 is further comprised of a series of tiles104 secured along the area of the channels 18 where the fan blade 16 andthe fan sides 14 are joined. Because this is the area of the fan 10subject to the most wear, the labyrinth seal 100 in this area mustreduce the friction wear caused by the solids in the gas or liquidstream more than in other areas in the fan 10. The extra layer of tiles104 in the labyrinth seal 100 creates a surface that causes turbulencethat breaks up the gas or liquid stream flow, and therefore slows downthe speed of the gas or liquid, and the speed of the suspendedparticles. Because the particles contact the surfaces at a slower speed,the wear in these areas is reduced such that it approximates to the wearin the other areas of the labyrinth seal 100. Additionally, like theplates, the individual tiles can move slightly in relation to eachother, therefore withstanding the torque experienced when the fan startsor stops without cracking or fracturing such as a single large surfacemight experience.

[0023] The tiles 104 are preferably of the same width and thickness. Inone arrangement of the present invention, as depicted in FIG. 3, tile104 is preferably of a length that is longer than tile 104′ by an amountequal to the thickness of the tiles. This enables creation of a sealedarea that has even edges by alternating tiles when installed asdescribed below. In an alternative arrangement of the present invention,as depicted in FIG. 4, the tiles 104 are all of approximately the samelength. When the seal is assembled, the edges are uneven. This type ofarrangement of tiles is typically used when it is necessary to reducethe flow stream turbulence further to diminish wear.

[0024] The tiles 104 are preferably laid side by side along the surfaceof the fan blade 16, and another row of tiles 104 is preferablypositioned side by side along the edge of the fan side 14. These tiles104 are secured to the edge of the fan blade 16 where it joins the fansides 14 in such a manner that the components project out beyond therest of the plates 102 along the area where the fan blade 16 and fansides 14 are joined.

[0025] As shown in detail in FIGS. 5 and 6, in one arrangement of thepresent invention, tile 104 is of a greater length than tile 104′. Onetile 104 is positioned on the fan blade 16 such that the end of the tile104 abuts the fan side 14, and the corresponding shorter tile 104′positioned along the fan side 14, has the end abutting tile 104. Eachadjacent set of tiles are preferably positioned in an alternatingpattern such that an end of the longer tile 104, positioned on the fanside 14 abuts the fan blade 16, and the corresponding shorter tile 104′,positioned along the fan blade 16 has an end abutting tile 104. Thisproduces edges and seams that form a path along which the gas or liquidstream flows.

[0026] As shown in detail in FIGS. 7 and 8, in an alternativearrangement of the present invention, all tiles 104 are of the samelength, width, and height. One tile 104 is positioned on the fan blade16 such that its end abuts the fan side 14, and the corresponding tile104 positioned along the fan side 14, has the end abutting first tile104. Each adjacent set tiles 104 are positioned such that the end of thefirst tile 104, positioned on the fan side 14 abuts the fan blade 16,and the corresponding tile 104 positioned along the fan blade 16 has theend abutting the first tile 104. This produces edges and seams that arenot smooth, and form a tortuous path along which the air stream flows.

[0027] Typically, the labyrinth seal 100 is composed of a wear-resistantmaterial, such as a metal carbide or ceramic. Such a material is moreresistant to the wear caused by the striking of suspended particles, andthus further increases the life of the fan 10. Because such materialstend to be more expensive than steel or aluminum alloys, it is moreeconomically feasible to make the entire fan out of a less expensivematerial, and only attach the more expensive wear-resistant sealmaterial to those parts which are subject to wear.

[0028] It is understood that the present invention can take many formsand embodiments. Accordingly, several variations may be made in theforegoing without departing from the spirit or the scope of theinvention.

[0029] Having thus described the present invention by reference tocertain of its preferred embodiments, it is noted that the embodimentsdisclosed are illustrative rather than limiting in nature and that awide range of variations, modifications, changes, and substitutions arecontemplated in the foregoing disclosure and, in some instances, somefeatures of the present invention may be employed without acorresponding use of the other features. Many such variations andmodifications may be considered obvious and desirable by those skilledin the art based upon a review of the foregoing description of preferredembodiments. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of theinvention.

What is claimed is:
 1. A rotating fan made of a first material having ahub through which a gas containing solid particles is drawn, the gas andsolid particles being projected out the circumference of the fan alongchannels formed by fan blades, the channels being lined with a labyrinthseal comprised of plates of a second material harder than the firstmaterial.
 2. The rotating fan of claim 1 wherein said labyrinth sealfurther comprises an additional layer of tiles securely attached alongat least one joint of the channel.
 3. A method for forming a protectivelabyrinth seal on at least some exposed areas of a rotating fan having ahub, sides and at least one fan blade, the method comprising: a)securing plates comprised of a hardened material to at least one face ofeach fan blade; b) affixing an additional layer of tiles of the hardenedmaterial having a face length, a side width, and an edge depth along atleast one intersection of the fan side and the fan blade such that: afirst face of a first tile is adjacent to the fan side and a first edgeof the first tile is adjacent to the plates on the face of the fanblade; a first face of a second tile is adjacent to the plates on theface of the fan blade, a first edge of the second tile is adjacent tothe side of the fan blade, and a portion of a first side of the secondtile is adjacent to a first side of the first tile; a first face of athird tile is adjacent to the plates on the face of the fan blade, afirst edge of the third tile is adjacent to a second face of the firsttile, and a portion of a first side of the third tile is adjacent to thefirst side of the second tile; a first face of a fourth tile is adjacentto the side of the fan, a first edge of the fourth tile is adjacent to asecond face of the second tile, and a portion of a first side of thefourth tile is adjacent to a first side of the first tile; and c)alternating the above configuration along the entire intersection of thefan side and the fan blade.
 4. The method of claim 3 wherein the platesand tiles are composed of a metal carbide.
 5. The method of claim 3wherein the plates and tiles are composed of a ceramic material.
 6. Themethod of claim 3 further comprising securing the plates and tiles tothe fan by means of an adhesive substance.
 7. The method of claim 3further comprising securing the plates and tiles to the fan by means ofbrazing.
 8. The method of claim 3 further comprising securing asubstrate between the fan blade and the plates.
 9. The method of claim 8further comprising securing the plates to the substrate and thesubstrate to the fan blade by means of an adhesive substance.
 10. Themethod of claim 8 further comprising securing the plates to thesubstrate and the substrate to the fan blade by means of brazing. 11.The method of claim 3 further comprising sealing along all exposed edgesof the tiles and plates adjoining the fan blade and fan side.
 12. Themethod of claim 3 wherein all tiles are of approximately a same length.13. The method of claim 3 wherein the length of the third and fourthtiles is shorter than the length of the first and second tiles by anamount approximately equal to a thickness of the tiles so that the edgesof the tiles projecting out from the joint are of approximately a sameheight.
 14. An apparatus for protecting at least one surface of arotating fan having a hub, sides and at least one fan blade, theapparatus comprising: a) plates comprised of a hardened material securedto at least a face of each fan blade; b) a layer of tile comprised ofthe hardened material secured to an intersection of the fan side and thefan blade, each tile having a face length, a side width and an edgedepth secured to the fan, the tile arranged such that: a first tile issecured to the fan with a first face adjacent to the side of the fan anda first edge adjacent to the plates on the face of the fan blade; asecond tile is secured to the fan with a first face adjacent to theplates on the face of the fan blade, a first edge adjacent to the sideof the fan blade, and a portion of a first side of the second tileadjacent to a first side of the first tile; a third tile is secured tothe fan with a first face adjacent to the plates on the face of the fanblade, a first edge adjacent to a second face of the first tile, and aportion of a first side of the tile adjacent to the first side of thesecond tile; a fourth tile is secured to the fan with a first faceadjacent to the side of the fan, a first edge adjacent to a second faceof the second tile, and a portion of the first side of the tile adjacentto the first side of the first tile; and c) tiles configured inaccordance with step b secured along the entire length of the joint ofthe fan blade and fan side.
 15. The apparatus of claim 14 wherein alltiles are of approximately a same length.
 16. The apparatus of claim 14wherein the length of the third and fourth tiles is shorter than thelength of the first and second tiles by an amount approximately equal toa thickness of the tiles so that the edges of the tiles projecting outfrom the joint are of approximately a same height.
 17. The apparatus ofclaim 14 wherein the pieces of hardened material are secured to theassembly by means of an adhesive substance.
 18. The apparatus of claim14 wherein the pieces of hardened material are secured to the assemblyby means of brazing.
 19. The apparatus of claim 14 further comprising asubstrate between the assembly and the plates of hardened material. 20.The apparatus of claim 19 wherein the plates of hardened material aresecured to the substrate, and the substrate to the assembly by means ofan adhesive substance.
 21. The apparatus of claim 19 wherein the platesof hardened material are secured to the substrate, and the substrate tothe assembly by means of brazing.
 22. The apparatus of claim 14 whereinall exposed edges of the tiles and plates adjoining the fan blade andfan sides are sealed.